Catheters having inflatable balloon attachments have been used for reaching small areas of the body for medical treatments, such as in coronary angioplasty and the like. Balloons are exposed to large amounts of pressure. Additionally, the profile of balloons must be small in order to be introduced into blood vessels and other small areas of the body. Therefore, materials with high strength relative to film thickness are chosen. An example of these materials is PET (polyethylene terephthalate), which is useful for providing a non-compliant, high-pressure device. Unfortunately, PET and other materials with igh strength-to-film thickness ratios tend to be scratch- and puncture-sensitive. Polymers that tend to be less sensitive, such as polyethylene, nylon, and urethane are compliant and, at the same film thickness as the non-compliant PET, do not provide the strength required to withstand the pressure used for transit in a blood vessel and expansion to open an occluded vessel. Non-compliance, or the ability not to expand beyond a predetermined size on pressure and to maintain substantially, a profile, is a desired characteristic for balloons so as not to rupture or dissect the vessel as the balloon expands. Further difficulties often arise in guiding a balloon catheter into a desired location in a patient due to the friction between the apparatus and the vessel through which the apparatus passes. The result of this friction is failure of the balloon due to abrasion and puncture during handling and use and also from over-inflation.
The present invention is directed to a non-compliant medical balloon suitable for angioplasty and other medical procedures and which integrally includes very thin inelastic fibers having high tensile strength, and methods for manufacturing the balloon. The fiber reinforced balloons of the present invention meet the requirements of medical balloons by providing superior burst strength; superior abrasion-, cut- and puncture-resistence; and superior structural integrity.
More particularly, the invention is directed to a fiber-reinforced medical balloon having long axis, wherein the balloon comprises an inner polymeric wall capable of sustaining pressure when inflated or expanded into a fiber/polymeric matrix outer wall surrounding and reinforcing the inner polymeric wall. The fiber/polymeric matrix outer wall is formed from at least two layers of fibers and a polymer layer. The fibers of the first fiber layer are substantially equal in length to the length of the long axis of the balloon and run along the length of the long axis. But “substantially equal in length” is meant that the fiber is at least 75% as long as the length of the long axis of the balloon, and preferably is at least 90% as long. The fiber of the second fiber layer runs radically around the circumference of the long axis of the balloon substantially over the entire length of the long axis. By “substantially over the entire length” is meant that the fiber runs along at least the center 75% of the length of the long axis of the balloon, and preferably runs along at least 90% of the length. The fiber of the second fiber layer is substantially perpendicular to the fibers of the first fiber layer. By “substantially perpendicular to” is meant that the fiber of the second fiber layer can be up to about 10 degrees from the perpendicular.
The invention is further directed to processes for manufacturing a non-compliant medical balloon. In one embodiment, a thin layer of a polymeric solution is applied over a mandrel, the mandrel having the shape of a medical balloon and being removable from the finished product. High-strength inelastic fibers are applied to the thin layer of polymer with a first fiber layer having fibers running substantially along the length of the long axis of the balloon and a second fiber layer having fiber running radially around the circumference of the long axis substantially over the entire length of the long axis. The fibers are then coated with a thin layer of a polymeric solution to form a fiber/polymeric matrix. The polymers are cured and the mandrel is removed to give the fiber-reinforced medical balloon.
In another embodiment of the invention, a polymer balloon is inflated and is maintained in its inflated state, keeping the shape of the balloon. High-strength inelastic fibers are applied to the surface of the balloon, with a first fiber layer having fibers running substantially along the length of the long axis of the balloon and a second fiber layer having fiber running radially around the circumference of the long axis substantially over the entire length of the long axis. The fibers are then coated with a thin layer of a polymeric solution to form a fiber/polymeric matrix. The fiber/polymeric matrix is cured to give the fiber-reinforced medical balloon, which can then be deflated for convenience, until use.
In a presently preferred embodiment, a thin coating of an adhesive is applied to the inflated polymer balloon or to the polymer-coated mandrel prior to applying the inelastic fibers.